Overload relay and magnetic switch assembly



y 1958 w. c. FURNAS 2,844,632

OVERLOAD RELAY AND MAGNETIC SWITCH ASSEMBLY 2 Sheets-Sheet 1 Filed July 8, 1957 IN VEN TOR.

)4 T 7-0 RNEXS.

United States Patent lice OVERLOAD RELAY AND MAGNETIC SWITCH ASSEMBLY William C. Furnas, Batavia Township, 111., assignor to Fnrnas Electric Company, Batavia, Ill., a corporation of Illinois Application July 8, 1957, Serial No. 670,488 8 Claims. (Cl. 200-88) This invention relates generally to improvements in electric switches, and it relates more specifically to improvements in the construction and operation of combined magnetic switch and overload relay assemblages for controlling diverse electric circuits.

The primary object of the present invention is to provide improved mechanism for effecting convenient and safe manipulation of a combined switch and overload assembly associated with the same electric circuit.

Many electric circuits have heretofore been provided with a main automatically functioning control switch, and 'with one or more overload relays, together with some means for holding the main control switch open while these relays were being reset after having been subjected to overload conditions. In cases where the main switch is of the electromagnetic type having an armature for actuatingthe movable switch contacts and wherein the overload relay was located near the armature, it has been proposed to provide a reset button adapted to maintain the fixed and movable switch contacts slightly separated while the relay was being reset, by inserting a thin plate between the cooperating poles of the field piece and armature of the electromagnet. While this type of safety device did to some extent hold the switch contacts apart during resetting of the overload relay-s, the thin insert plate did not insure sufficient separation to positively prevent possible arcing across the fixed and movable contacts, and the use of a heavier insert plate is objectionable due to the added weight and other complications involved.

It is therefore a more specific important object of this invention to provide a simple and compact assemblage for positively holding the main switch contacts separated or open to theirfullest extent whenever the cooperating overload relay or relays are being reset.

Another important object of the invention is to provide an improved overload relay and magnetic switch assembly which is light but durable in structure, but highly reliable in operation.

A further important object of my invention is to provide'an improved overload reset and switch combination, which is conveniently operable with utmost safety.

Still another important object of the present invention is to provide an improved overload relay resetting device which can be readily associated with most standard magnetic switches to provide a compact combined unit.

These and othermore specific objects and advantages of the invention will be apparent from the following detailed description. 7

A clear conception of the features constituting the present improvement, and of the construction and operation of a typical commercial electromagnetic switch unit embodying the invention, may be had by referring to drawings accompanying and forming a part of this specification wherein like reference characters designate the same or similar parts in the various Views.

Fig. 1 is afront view of the magnetic switch and duplex overload relay assembly with the armature lowered 2,844,682 Patented July 22, 1958 to maintain the switch contacts separated and the relay resent member in normally released position;

Fig. 2 is a transverse horizontal section through the switch and relay assemblage of Fig. 1, taken along the irregular line 2--2 of Fig. 1;

Fig. 3 is a vertical section through the same unit, taken along the irregular line 3-3 of Fig. l, but showing the magnet armature positively held in lowermost position so as to maintain the switch contacts separated to the maximum extent while the overload relays are being reset; and

Fig. 4 is another vertical section through the unit similar to that of Fig. 3, but showing the main switch contacts in closed position and the relay resetting member in inactive or released position;

While the invention has been illustrated and described herein as having been incorporated in a switch unit embodying an electromagnetic switch of the improved type shown in the pending U. S. application Serial No. 578,288, filed April 16 1956, and also utilizing overload relays of the type covered'by U. S. Patent No. 2,597,068, granted May 20, 1952, it is not the intent to necessarily restrict the use of the improved features to such specific switches and relays; and it is also contemplated that specific descriptive terms employed herein be given the broadest possible interpretation consistent with the actual disclosure.

Referring to the drawings, the electric circuit control assemblage shown therein by way of illustration, comprises in general, an upright support 6; an arc box or contact housing 7 secured to the upper portion of the support 6 and having therein four pairs of stationary contacts 8; an electromagnet having a field piece 9 mounted on the support '6 below the arc box 7 and provided with an energizing coil 10, and also having a magnetic armature 11 reciprocable vertically within the coil 10 and provided with spaced bottom extensions 12; a U-shaped pusher 13 having side arms 14 extending upwardly along the opposite sides of the coil 10 and field piece 9, and also having its lower cross-piece pivotally connected to the armature extensions 12 by a transverse pin 15 and provided with a forwardly and downwardly inclined flange 16; a transverse cross-bar 17 secured to the upper ends of the pusher arms 14 and carrying four pairs of movable contacts 18 adapted to cooperate with the adjacent stationary contacts 8 .within the arc box 7; a thermal overload relay 19 secured to the support 6 on each side of .the magnet and pusher assembly, and each having a downwardly projecting reset plunger 20; an elongated horizontal reset member 21 for both relays 19 reciprocable longitudinally between the relays and having a medial wedge 22 cooperable with the inclined flange 16 of the pusher 13; and a bell crank 23 pivoted on a rigid lower bracket portion of the support 6 and having opposite end arms 24 cooperable with the adjacent relay plungers 20 and also having a bail shaped medial arm 25 connected to the inner end of the reset member 21.

The main support 6 may be formed of sheet metal and for mounting within a suitable casing, and the front of the support is provided with an upright plate 27 in which the stem of the reset member 21 is guided for reciprocation as shown in Figs. 1, 3 and 4, and which may also be utilized as a supportfor a manually operated control switch for the electric circuit which is normally automatically controlled by the magnetic switch and the overload-relays. The arc box or contact housing is constructed of insulation and is provided with a series of upright partitions 28 forming segregated chambers within which the several pairs of cooperating fixed and movable contacts 8, 18 are confined; and the stationary contacts have terminal screws 29 associated therewith and which are all accessible from the front of the switch as-, semblage. The field piece 9 and the armature 11 of the electromagnet are formed of ferrous laminations, and the armature 11 is guided for vertical reciprocation within the energizing coil and has lateral poles 34) adapted to coact with lower poles 31 formed on the field piece 9.

The U-shap'ed pusher 13 is also preferably formed of resilient sheet metal, and the side arms 14 of this pusher are spaced from the adjacent sides of the field piece 9 and coil 10 but may be guided for vertical reciprocation near the movable contact carrying bar 17 by means of a horizontal guide plate 33 formed of insulation. Since the lower portion of the pusher 13 is pivotally attached by means of the pin 15 to the depending extensions 12 of the armature 11 and only the upper ends of the pusher side arms 14 are guided in the plate 33, these resilient arms are capable of deflecting and thereby absorbing shock and vibration due to sudden starting and stopping of the armature 11 and thus relieving the movable contacts 18 which are carried by the bar 17 from such shock and resultant vibration and noise. The lower downwardly and forwardly inclined flange 16 is formed integral with the pusher 13 and bears directly on the pin 15 between the rigid armature extensions 12, so that any downward pressure exerted upon the flange 16 will positively hold the armature 11 in its lowermost position and will also maintain the movable switch contacts 18 separated from the stationary contacts 8 to the maximum extent.

The thermal overload relays 19 which are attached to the support 6 on opposite sides of the electromagnet, are of well known construction, and are also spaced from the pusher arms 14 as shown in Fig. 1. As previously indicated, the relays 19 may be of the type covered by U. S. Patent No. 2,597,068, and each of these relays embodies a solder pot 35 surrounded by a heating coil 36 which is connected in the electric circuit of the magnetic switch, the solder pot 35 being interconnected with the reset plunger 24) by a spindle and ratchet mechanism in such manner that whenever the coil 36 is heated sulficiently to melt the solder the flow of electric current through the relay 19 will be interrupted. After the overload condition has ceased and the solder has solidified, the plunger 20 may be forced inwardly as depicted in Fig. 3 to reset the relay, but these plungers 20 are automatically retained in their outermost positions as in Fig. 1 when no overload conditions exist.

The elongated reset member 21 which is guided for reciprocation in the front upright plate 27 is also formed of insulation and has its inner end provided with a lost motion slot 38 coacting with the bail shaped medial arm of the bell crank 23 as shown in Figs. 3 and 4, while its outer end 39 serves as a pushbutton. The bell crank 23 may be formed by heavy wire and is pivotally mounted in a lower bracket 40 formed of sheet metal and which is rigidly attached to the support 6, and the outer end arms of this bell crank are slightly curved for better engagement with the overload relay plungers 20 when the member 21 is pushed inwardly to reset the relays 19. The wedge 22 of the pushbutton member 21 is engageable with the pusher flange 16 whenever this member is forced inwardly; but the member 21 is normally urged outwardly with the wedge 22 in stopping engagement with a fastener of the plate 27 as in Fig. 4, by means of a leaf spring 41 the mid-portion of which is secured by a hook flange 42 to the bracket 40 and the opposite ends of which bear against the bell crank arms 25.

When the improved switch unit has been constructed and assembled as hereinabove described, and has been installed in an electric circuit, the reset member 21, bell crank 23, and relay plungers 20 will normally be in inactive position as illustrated in Fig. 4 so that the electromagnet will be free to automatically move the movable contacts 18 into or out of engagement with the stationary contacts 8. However, whenever the circuitis subjected to excessive overload, the relays 19 will immediately function to break the same thereby de-energizing the coil 10 of the magnet and causing the armature 11 to drop into its lowermost position as in Fig. 3, thereby separating the contacts 18 from the contacts 8 to the maximum extent. When the overload condition has subsided and the solder pots 35 have cooled, the reset member 21 may be pushed inwardly as in Fig. 3 to cause the bell crank 23 to lift both reset plungers 20 so as to reset the relays 19, while simultaneously causing the wedge 22 of the member 21' to engage the inclined flange 16 of the movable contact pusher 13 and thereby positively holding the switch contacts 8, 18 separated to the maximum extent. After the relays 19 have been thus reset and the pressure applied to the pushbutton end 39 of the member 21 is released, the spring 41 quickly restores the bell crank 23 and the reset member 21 to the inactive position of Fig. 4, thereby permitting continued automatic functioning of the main magnetically actuated switch.

From the foregoing detailed description of the construction and operation of the device, it will be apparent that the invention in fact provides an overload relay and magnetic switch assembly wherein the main switch contacts 8, 18 are positively held separated or out of engagement to the maximum extent whenever the relays 19 are being reset and until normal operating conditions have been re-established. The improved mechanism is simple and compact in structure, and dependable in action and definitely avoids possible flow of current through the main switch as long as overload conditions prevail. All elements of the improved assemblage are of sturdy construction and well insulated, and may also be conveniently assembled and installed in relatively standard switches, and the device has proven highly satisfactory and successful in actual use.

It should be understood that it is not desired to limit this invention to the exact details of construction and operation of the magnetic switch and overload relay assembly, herein specifically shown and described, for various modifications within the scope of the appended claims may occur to persons skilled in the art.

I claim:

1. An electric circuit control assemblage comprising, a support, fixed switch contacts mounted upon said support, movable switch contacts cooperable with said fixed contacts to make and break the circuit, an electromagnet also mounted upon said support and having an armature for reciprocating said movable contacts, means operatively connecting said armature with said movable contacts and having thereon an inclined surface, an overload relay likewise mounted upon said support and being provided with a reset plunger, and a reset plunger actuating member having thereon a wedge cooperable with said inclined surface to positively hold said movable contacts separated from said fixed contacts to the maximum extent whenever said relay is being reset.

2. An electric circuit control assemblage comprising, a support, fixed switch contacts mounted upon said support, movable switch contacts cooperable with said fixed contacts to make and break the circuit, an electromagnet also mounted upon said support and having an armature for reciprocating said movable contacts, an overload relay likewise mounted upon said support and being provided with a reset plunger, a bell crank pivotally suspended from said support and having one arm cooperable with said plunger to reset said relay, and a reset plunger actuating member coacting with the other arm of said bell crank and having a wedge cooperable with said armature to positively hold said movable contacts separated from said fixed contacts tojthe maximum extent whenever said member is actuated to reset said relay.

3. An electric circuit control assemblage comprising, a support, fixed switch contacts mounted upon said support,

movable switch contacts cooperable with said fixed contacts to make and break the circuit, an electromagnet also mounted upon said support and having an armature for reciprocating said movable contacts, an overload relay likewise mounted upon said support and being provided with a reset plunger, a bell crank pivotally suspended from said support and having one arm cooperable with said plunger to reset said relay, a reset plunger actuating member coacting with the other arm of said bell crank and having a wedge cooperable with said armature to positively hold said movable contacts separated from said fixed contacts to the maximum extent whenever said member is actuated to reset said relay, and resilient means coacting with said bell crank to release said plunger and said armature whenever said member is inactive.

4. An electric circuit control assemblage comprising,

a support, fixed switch contacts mounted upon said support, movable switch contacts cooperable with said fixed contacts to make and break the circuit, an electromagnet also mounted upon said support and having an armature for reciprocating said movable contacts, a pusher connecting said armature with said movable contacts and having an inclined portion adjoining the armature, an overload relay likewise mounted upon said support and being provided with a reset plunger, and a reset plunger actuating member having a wedge cooperable with said inclined pusher portion to positively hold said movable contacts separated from said fixed contacts to the maximum extent whenever said relay is being reset.

5. An electric circuit control assemblage comprising, a support, fixed switch contacts mounted upon said support, movable switch contacts cooperable with said fixed contacts to make and break the circuit, an electromagnet also mounted upon said support and having an armature for recpirocating said movable contacts, a pusher surrounding said electromagnet and connecting said movable contacts with said armature, said pusher having an integral inclined portion pivotally attached to the armature, an overload relay likewise mounted upon said support and being provided with a reset plunger, and a reset plunger actuating member having a Wedge cooperable with said inclined pusher portion to positively hold said movable contacts separated from said fixed contacts to the maximum extent whenever said relay is being reset,

6. An electric circuit control assemblage comprising, a support, fixed switch contacts mounted upon said support, movable switch contacts cooperable with said fixed contacts to make and break the circuit, a magnet also mounted upon said support and having an armature for reciprocating said movable contacts, a U-shaped pusher having resilient side arms spaced from said magnet and connecting said armature with said movable contacts and also having an inclined portion adjoining and pivotally attached to the armature, a overload relay likewise mounted upon said support and being provided with a reset plunger, and a reset plunger actuating member having a wedge cooperable with said inclined pusher portion to positively hold said movable contacts separated from said fixed contacts to the maximum extent Whenever said relay is being reset.

7. An electric circuit control assemblage comprising, a support, fixed switch contacts mounted upon said support, movable switch contacts cooperable with said fixed contacts to make and break the circuit, a magnet also mounted upon said support and having an armature for reciprocating said movable contacts, a pusher surrounding said electromagnet and connecting said movable contacts with said armature, said pusher having an integral inclined portion pivotally attached to the armature, an overload relay likewise mounted upon said support on each side of said magnet and each being provided with a reset plunger, and a reset plunger actuating member for both relays having a wedge cooperable with said inclined pusher portion to positively hold said movable contacts separated from said fixed contacts to the maximum extent whenever said relays are being reset.

8. An electric circuit control assemblage comprising, a support, fixed switch contacts mounted upon said support, movable switch contacts cooperable with said fixed contacts to make and break the circuit, a magnet also mounted upon said support and having an armature for reciprocating said movable contacts, an overload relay likewise mounted upon said support on each side of said magnet and being provided with a reset plunger, a bell crank pivotally suspended from said support and having an end arm cooperable with each reset plunger and also having a medial bail shaped arm, a reset plunger actuating member coacting with said medial bell crank arm and having a wedge cooperable with said armature to positively hold said movable contacts separated from said fixed contacts whenever said member is actuated to reset said relay, and a leaf spring coacting with said end bell crank arms to release said plungers and said armature Whenever said member is inactive.

References Cited in the file of this patent UNITED STATES PATENTS Re.20,094 Wilms Sept. 1, 1936 1,901,512 Harris Mar. 14, 1933 2,371,601 Beeman Mar. 20, 1945 2,473,196 Dannenberg June 14,- 1949 2,597,068 Cobb u May 20, 1952 

